1. Field of the Invention
The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a polishing apparatus having a cleaning apparatus for cleaning a polished workpiece.
2. Description of the Related Art
In semiconductor device manufacturing processes, semiconductor wafers are polished to a flat mirror finish in a semiconductor wafer fabrication process, and layers formed on semiconductor devices are polished to a flat mirror finish in a semiconductor device fabrication process. These polishing processes in the semiconductor wafer fabrication process and the semiconductor device fabrication process are performed by a polishing apparatus.
Conventionally, such a polishing apparatus has been designed as a dedicated polishing apparatus having a single function of polishing semiconductor wafers. The semiconductor wafers which have been polished by the polishing apparatus are transported to a next cleaning process by a movable container in which they are immersed in water to keep them from drying during transportation. However, the cleaning process tends to impair the cleanliness of a clean room, and the polished semiconductor wafers need to be transported by an operator or a manually operated transportation means. Further, a large installation space is required for two kinds of apparatuses comprising the polishing apparatus and a cleaning apparatus that is used to carry out the subsequent cleaning process.
In an effort to make the polishing process clean and reduce the installation space of the apparatus, there has been developed a polishing apparatus which performs both a polishing process and a cleaning process and which is of a dry-in and dry-out type for introducing semiconductor wafers therein in a dry condition and removing polished and cleaned semiconductor wafers therefrom in a dry condition. However, the dry-in and dry-out type polishing apparatus has a lower processing capability per unit time and unit installation area than the conventional dedicated polishing apparatus having a single function of polishing the semiconductor wafers. A polishing apparatus designed for solving the above problem has been proposed by Japanese patent application No. 11-59522, and offers many advantages over the conventional dedicated polishing apparatus.
The dry-in and dry-out type polishing apparatus has two cleaning apparatuses operable based on two different cleaning methods for cleaning semiconductor wafers which have been polished, in order to increase the processing capability per unit installation area. Such two cleaning apparatuses clean a semiconductor wafer in two stages, and are installed in a smaller installation area with minimum cleaning functions. However, as recent semiconductor devices have smaller circuit elements and finer interconnections in integrated patterns, there has been a demand for removing polished semiconductor wafers from the polishing apparatus in a higher level of cleanness, and therefore the cleaning stages for cleaning the polished semiconductor wafers have increased from two stages to three stages to meet such a demand. Specifically, such three cleaning stages include a process of removing fine particles attached to the polished semiconductor wafer, a process of removing metal ions attached to the polished semiconductor wafer, and a process of drying the clean polished semiconductor wafer. In some cases, two or more types of metal ions attached to the polished semiconductor wafer are removed by different chemicals supplied thereto, with the result that a total of four stages are involved in cleaning the polished semiconductor wafer. The four cleaning stages may be performed by respective four cleaning apparatuses, or two stages of the four cleaning stages may be performed by one of three cleaning apparatuses.
If three or more cleaning stages are carried out by two cleaning apparatuses, then two cleaning stages are performed by at least one cleaning apparatus, whose processing capability is thus reduced per unit time. If three or more cleaning apparatuses are provided in a row in a polishing apparatus, then the polishing apparatus becomes large in size, and has a reduced processing capability per unit time. Either one of these arrangements is detrimental to the advantages offered by the concept in Japanese patent application No. 11-59522.
It is therefore an object of the present invention to provide a polishing apparatus which can be used as a dry-in and dry-out type polishing apparatus, has a high processing capability per unit time and unit installation area, has three or more cleaning stages in a cleaning process, and is capable of making semiconductor wafers cleaner to meet requirements for smaller circuit elements and finer interconnections on semiconductor devices.
A further object of the present invention is to provide a polishing apparatus which can be used as the dry-in and dry-out type polishing apparatus and is capable of greatly increasing a processing capability of workpieces such as semiconductor wafers per unit time and unit area.
To achieve the above objects, according to a first apparatus comprising a turntable having a polishing surface, a top ring for holding a workpiece and pressing the workpiece against the polishing surface to polish the workpiece, at least three cleaning apparatuses for cleaning polished workpieces, and a transfer structure for transferring the polished workpieces between the at least three cleaning apparatuses. The transfer structure is capable of changing transfer routes between the at least three cleaning apparatuses. The transfer structure comprises a plurality of robots.
According to the present invention, the polishing apparatus can change transfer routes to comply with the required cleaning processes for maintaining a desired number of cleaning stages depending on various polishing processes without reducing the processing capability per unit installation area, and also to shorten the processing time of each of the cleaning processes by assigning the cleaning process which needs a long period of time to at least two cleaning apparatuses, thereby increasing the number of processed workpieces per unit time, i.e., throughput.
According to a second aspect of the present invention, there is provided a polishing apparatus comprising a plurality of turntables having respective polishing surfaces, a plurality of top rings for holding workpieces and pressing the workpieces against the polishing surfaces to polish the workpieces, a rotary transporter disposed in a position which can be accessed by the top rings and having a plurality of portions positioned on a predetermined circumference from a center of rotation of the rotary transporter for holding the workpieces, the rotary transporter being capable of replacing the workpieces placed at the portions, a pusher for transferring the workpieces between the rotary transporter and the top rings, and a reversing device for transferring the workpieces to and from the rotary transporter and reversing the workpieces.
It is possible to shorten the time required to transfer a work piece to be polished, such as a semiconductor wafer, to the top ring, for thereby greatly increasing the number of processed workpieces per unit time, i.e., throughput.
According to a third aspect of the present invention, there is provided a polishing apparatus comprising a polishing section for polishing a workpiece, a cleaning section for cleaning a polished workpiece, and a reversing device for reversing a workpiece to be polished and a polished workpiece. The polishing section is arranged to polish a workpiece while a surface thereof being polished is directed downwardly, and the cleaning section is arranged to clean said polished workpiece while a polished surface thereof is directed upwardly.
In the cleaning processes, the polished surfaces of workpieces can be processed while the polished surfaces are being directed upwardly.
According to a fourth aspect of the present invention, there is provided a polishing apparatus comprising a turntable having a polishing surface, a top ring for holding a workpiece and pressing the workpiece against the polishing surface to polish the workpiece, a plurality of cleaning apparatuses for cleaning polished workpieces, and a workpiece station having workpiece supports for holding workpieces in a standby state while the workpieces are cleaned in a plurality of stages through the cleaning apparatuses.
Inasmuch as polished workpieces can wait while being processed in cleaning processes, a plurality of cleaning processes having different processing times can be performed parallel to each other on a plurality of polished workpieces.
According to a fifth aspect of the present invention, there is provided a polishing apparatus comprising a loading and unloading section for supplying a workpiece to be polished and receiving a polished workpiece, a polishing section for polishing the workpiece, and a cleaning section for cleaning the polished workpiece. Chambers separated by partitions have respective openings for allowing the workpiece to pass therethrough. The loading and unloading section, the polishing section, and the cleaning section are housed in the chambers.
Since the chambers in which the cleanliness of the atmosphere is different from one another are separated by the partitions, the atmosphere in a contaminated chamber is prevented from flowing into a clean chamber and hence from lowering the cleanliness in the clean chamber.
According to a sixth aspect of the present invention, there is provided a polishing apparatus comprising a plurality of turntables having respective polishing surfaces, a plurality of top rings for holding workpieces and pressing the workpieces against the polishing surfaces to polish the workpieces, a plurality of cleaning apparatuses for cleaning polished workpieces, and a transfer structure for transferring the workpieces. The polishing surfaces include a polishing surface for primarily polishing the workpiece and a polishing surface for finish polishing the workpiece.
The polishing surface for polishing the workpiece to produce a polished surface at a higher polishing rate and the polishing surface for polishing the workpiece to produce a finer polished surface in the finish manner at a lower polishing rate are combined with each other to efficiently polish the workpiece to produce a well polished surface thereof.
According to a seventh aspect of the present invention, there is provided a polishing apparatus comprising a loading and unloading section for supplying a workpiece to be polished and receiving a polished workpiece, a turntable having a polishing surface, a top ring for holding a workpiece and pressing the workpiece against the polishing surface to polish the workpiece, at least three cleaning apparatuses for cleaning polished workpiece, at least two of the three cleaning apparatuses having an identical cleaning function, and a transfer structure for transferring the workpieces.
Of the three cleaning apparatuses, at least two of the cleaning apparatuses have identical cleaning modules. Consequently, cleaning processes which need to be performed over a long period of time can be carried out by two or more cleaning apparatuses, i.e., a cycle time can be distributed, to increase the number of processed workpieces per unit time, i.e., throughput.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, which illustrate preferred embodiments of the present invention by way of example.